For horse owners, the arrival of Spring is synonymous with tapeworm treatment. In general, horse owners in the UK have willingly adopted a strategic approach to worming based on faecal eggs counts (FEC). However, many are reluctant to adopt the same approach to tapeworms and continue to treat twice annually in spite of not having information about the infection status of their animal. On continuation, I provide some information about this common parasite, and best practice methods to address it.

The Equine Tapeworm

There are a number of species of tapeworm in the UK which are capable of infecting horses; however most of these are rare. The tapeworm species most commonly found in the horse is Anoplocephala perfoliata. It can reach up to 8cm in length and attaches itself to the intestinal lining at the ileocaecal junction which is where the small intestine meets the large intestine. It Is a perfect location for the tapeworm because the digestive juices found here are rich in the nutrients which it needs to thrive.

How Common is Tapeworm Infection?

It is impossible to be certain of infection rates due to the difficulty in detecting infection but studies suggest up to 69%1 of horses in the UK are infected at any given time.

A horse can become infected at any age; however tapeworm tends to have a bigger impact on very young and very old horses as their immune systems are not as robust.

Life Cycle

The tapeworm has an indirect life cycle which means that it requires more than one host to reach adulthood and reproduce.

The intermediate host for the most common equine tapeworm (A.perfoliata) is the forage mite (Oribatid mite). Forage mites are found on pasture and play a vital role in maintaining good quality grazing. The mites themselves pose no threat to your horse but the tapeworm cysts which they carry can.

Your horse can ingest forage mites when grazing at pasture or from conserved forage such as hay. If these forage mites are infected they can transmit the tapeworm cyst to your horse. The cyst is then ‘digested’ to free the infective tapeworm which attaches to the intestinal lining at the ileocaecal junction.

As the tapeworm grows it develops body segments, andonce it reaches sexual maturity these segments fill with eggs and are shed in the faeces. It takes 6-10 weeks after the horse ingests the cyst for the tapeworm to begin shedding eggs.

Clinical Signs of Tapeworm Infection

It benefits the tapeworm to cause as little damage to its host as possible, in order to ensure it maintains its source of nutrition. For many years it was believed that tapeworms cause no real problems in horses. However, more recent studies have shown that they can be linked to spasmodic colic, impaction at the ileocaecal junction, ileocaecal intussusception, intestinal ulcers and peritonitis.

Your horse may be infected with tapeworm and show no symptoms at all. In more severe infections they may have some of the following clinical signs:

Diarrhoea

Dull Coat

Poor Growth

Intermittent Colic Episodes

Poor performance

General Lethargy

Diagnostics

We know from the tapeworm life cycle that when the tapeworm sheds its eggs they are dispersed in a segment of its body called the proglottid. If the proglottid remains intact then no eggs will be found in the faeces in spite of the horse being infected. As a result tapeworm eggs are rarely detected in faecal egg counts (FEC) even if the horse is infected.

The best approach is to carry out a test called an ELISA antibody test. When a horse becomes infected with tapeworm it will produce antibodies to try and protect itself. The ELISA test is capable of detecting these antibodies. It could previously only be carried out on a blood sample but can now be carried out on saliva making it much more accessible and cost effective. The antibodies persist for months after an infection so a positive result tells us that the horse has been exposed to tapeworm recently. A positive result and a lack of recent tapeworm treatment allows us to assume that the horse is infected.

Treatment

Ideally you should carry out an ELISA test before treating for tapeworm to help protect our wormers from resistance.

If you are unable to test you should carry out tapeworm treatment once in the Spring and once in the Autumn.

The two active ingredients which can treat tapeworm infection are Pyrantel Embonate (double dose) and Praziquantel. Table 1 details the activity of the anthelmintics which are available to treat tapeworm in horses.

Remember to give your horse the correct dose for its weight - you can use a weigh bridge or a weigh tape to determine the dose required. Repeatedly exposing parasites to the same class of anthelmintic is known to speed up the rate of resistance so try to rotate the class of active ingredient which you use. Remember to consider which parasites you are trying to target and select the most appropriate active ingredient based on that.

If you are uncertain please speak to your vet or SQP as they will be able to give you the best advice for your circumstances.

Table 1

Parasites Treated

Pyrantel

Praziquantel

Ivermectin/ Praziquantel

Moxidectin/ Praziquantel

Tapeworm

✓*

✓

✓

✓

Small Strongyles

✓

X

✓

✓

Encysted Small Redworm

X

X

X

✓

Large Strongyles

✓

X

✓

✓

Large Roundworms

✓

X

✓

✓

Pinworm

✓

X

✓

✓

Habronema muscae

X

X

✓

✓

Hair Worms (Trichostrongylus axei)

X

X

✓

✓

Bot Fly

X

X

✓

✓

Neck threadworms (Onchocerca spp)

X

X

✓

X

Intestinal threadworms (S. westeri)

X

X

✓

✓

Lungworm

X

X

✓

X

*Pyrantel must be administered at a double dose to effectively treat tapeworms

References

D.W.Jagger et el (1988). “Prevalence of Anoplocephala perfoliata in horses and ponies in Clwyd, Powys and adjacent English marches” Vet Record 123 562-3

Care should be taken to avoid the following practices because they increase the risk of development of resistance and could ultimately result in ineffective therapy:

Too frequent and repeated use of anthelmintics from the same class, over an extended period of time

Under dosing; this may be due to underestimation of body weight or mis-administration of the product.

This information was provided by Bimeda- makers of Bimectin Equine and Embotape*

*Bimectin Equine (18.7mg/g Ivermectin) is a POM-VPS medicine. Embotape (11.4g/syringe Pyrantel Embonate) is a POM-VPS medicine. For full product information including dose rates, see the SPC data sheet on the VMD website or the data sheet on the Bimeda Website (Bimeda.co.uk) Use Medicines Responsibly. Noah.co.uk

About the Author:

Rachel Mallet, BVM&S MRCVS, is a qualified Veterinary Surgeon, who now works as a Professional Services Vet; providing technical support to vets, SQPs and horse owners in the UK. Rachel is passionate about animal health and about promoting best practice among animal health professionals and horse owners. Here, Rachel talks about the best-practice approach to addressing a parasite which all horse owners will be familiar with tapeworm.

Deficiency of iodine can often come as a surprise to producers following a bad calving season. Adult animals can appear to cope relatively well for extended periods of time in spite of being deficient in iodine. While they may appear clinically healthy to the naked eye, regular monitoring of performance indicators would give an early warning that action and investigation may be appropriate.

Ideally farmers should be scheduling regular monitoring of trace element blood status into their herd health plan in late pregnancy (approximately 3 months pre-calving). This would allow them to take action while disease is sub-clinical and before more serious production losses are accrued.

Iodine is a component of the thyroid hormones which regulate the rate of metabolism and increase the rate of absorption of carbohydrate from the gastrointestinal tract. Thyroxine (T4) is produced in the thyroid gland and circulated to the body tissues. A selenium dependent enzyme is required to convert it to the active Tri-iodothyronine (T3). This is why selenium and iodine deficiencies can be interlinked.

As adult animals can cope so well in spite of being deficient generally the first clinical signs of deficiency are noted in the new-borns. This is because the foetus requires a supply of iodine to support brain, heart and lung development.

Ruminants cannot store iodine indefinitely so are susceptible to deficiency during periods of reduced dietary intake or increased demand (such as during pregnancy). Any excess iodine which the animal cannot utilise will be excreted primarily in the urine with a small amount excreted via the milk in lactating animals.

Indicators of Iodine Deficiency Include:

Abortion

Still born calves

Hairless calves

Weak calves slow to stand and suckle

Cows may retain afterbirth

Reduced fertility

Goitre (enlarged thyroid)

Trace Elements Also Important During Gestation

Iodine isn’t the only important trace element for the gestation period and it’s important to be aware of other critical trace elements.

For example, Selenium plays a role in the immune system, fertility, muscle tissue health and iodine utilisation. Animals deficient in selenium can give birth to calves affected by white muscle disease which occurs when the muscle tissue becomes damaged and unable to function. Deficiency of selenium is also a risk factor for retained foetal membranes which can increase the time taken to get back into calf.

Copper is the trace element which gets the most attention in terms of reproduction. Copper is an essential component of a number of different enzymes which allows the animal to thrive including enzymes responsible for energy utilisation and fertility.

How Can Farmers Tell If Stock Are Deficient?

Farmers should work with their vet to determine which, if any, trace element imbalances are present within their herd. This is very important because there is no benefit to giving additional trace element supplementation where no deficiencies exist and it may even harm your cattle. Selenium and copper in particular can be dangerous if over supplied.

Forage is incredibly variable from both field to field and year-on-year. Variations in diet can cause animal status to change. Analysing forage, in conjunction with blood sampling, is the best way to determine trace element status. If liver samples can also be obtained for analysis then this gives the greatest information.

From a commercial aspect there are two main considerations which justify the importance of investigation:

Farmers could be spending money on trace elements which are not required

Farmers could be losing animal productivity to sub-clinical disease.

Sub-clinical trace element deficiencies are not severe enough to be visualised by eye but will have an impact on the productivity of the animals. If farmers wait until the deficiency is so severe that clinical signs have appeared, they will already be out of pocket.

Which Form Of Trace Element Supplementation Is Best?

There is an array of different forms of trace element supplementation available and it can be difficult to know which is best for herds. Let’s take a look at the advantages and disadvantages of some of the most popular methods:

Oral DrenchesDrenches can be a cheap and convenient option however they are relatively short acting and repeated doses mean greater labour. For trace elements which cannot be stored in the body, such as iodine or cobalt, they are not appropriate to treat deficiencies. A form of continuous supplementation must be supplied, which is especially important for in-calf cows and their developing foetuses.

Free Access Systems, Such as Licks and BlocksWhere a need to supplement trace elements has been established, we need to ensure that all animals receive an amount of trace elements which is compatible with their daily requirements. Too much of a trace element can prove toxic; too little and the deficiency will not be addressed.

Unfortunately, the free access lick and block systems do not provide this guarantee and an independent study highlighted that intakes between animals are extremely variable, with some consuming nothing and others consuming excessive quantities.1 A more scientific approach to supplementation is required.

InjectionsInjections can be suitable for targeted administration in conjunction with the advice of your vet. They can be appropriate where only a single trace element, such as copper or selenium is required.

In Feed SupplementationTrace elements can be provided by the provision of TMR, concentrates or bag minerals. Often these are specified based on ‘averages’ or ‘common requirements’ as opposed to being based on what has been determined is deficient and required on farm. Ideally these mixes should be prepared based on an investigation in to the animals’ trace element status and requirements. This method can add significantly to the cost of production and can be difficult for extensively managed cattle.

Trace Element BolusesBoluses provide an convenient, cost-effective and controlled method of trace element supplementation. Bimeda soluble glass bolus CoseIcure cattles provides exactly the same amount of copper, cobalt, selenium and iodine every single day for up to 6 months in cattle.. This means there are no variable intakes and no variation between animals. The continuous, controlled release of the bolus is particularly important for animals requiring cobalt and iodine which cannot be stored in the body and therefore a daily supply is required. Their long-lasting nature is also highly convenient and reduces labour costs as regular bolusing is not required.

Key Points:

Blood testing in conjunction with forage analysis in the simplest way to obtain information on the animals trace element status

Deficiency of trace elements can cause poor productivity but there are many other causes which your vet may advise you also investigate

Over supplementation does not improve productivity and can be dangerous, particularly where selenium and copper are concerned.

Establish the need before supplementing with trace elements

Pay particular attention to stock in late pregnancy as deficiencies in trace elements can have serious implications for both cow and calf.

CoseIcure cattle bolus contains copper, cobalt, selenium and iodine and lasts up to 6 months in cattle.Before supplementing trace elements, particularly copper and selenium which can be toxic, it is recommended that you seek advice from a vet or nutritionist.

About the Author Rachel Mallet is a Veterinary Surgeon, who now works as a Professional Services Vet providing technical support to vets, SQPs and farmers in the UK. Rachel is passionate about animal health and about promoting best practice and preventative medicine amongst farmers.